Air drying resins or binders are known primarily in the field of alkyd resins; water dilutable alkyd resins are obtained by mixing (unmodified) alkyd resins with emulsifiers or by incorporation of a sufficient number of acid groups into the polyester molecule which remain following the condensation reaction, and the neutralisation of at least some of said groups, or cocondensation with hydrophilic polyoxyalkylene polyols such as polyethylene glycol. The former systems are anionic, the latter systems are non-ionic in nature.
By way of example, hydroxy functional emulsifiers for alkyd resins based on polyurethane polyureas have been known from EP 0 741 156 A1. Other externally emulsified aqueous alkyd resin compositions have been described in EP 0 593 487 A1. Alkyd resins with chemically incorporated emulsifier which are self-emulsifying have been known from EP 0 312 733 A2.
Water compatibility is achieved in all cases by the use of nonionic or anionic emulsifiers, in chemically incorporated or added form.
It is also known to modify polyurethane resins by incorporating unsaturated fatty acids (EP 0 444 454 A2) so that paints produced with them are air drying.
Epoxy functional resins which, through modification with fatty acids, lead to air drying binders have been described in EP 0 355 761 A2 (esters of fatty acids with epoxy resins), EP 0 316 732 A2, EP 0 370 299 A1 (acrylate resins with epoxide groups), and EP 0 267 562 A2 (alkyd, urethane-alkyd or epoxide-ester resins grafted in an aqueous medium with olefinically unsaturated monomers).
Aqueous formulations of neutralised reaction products of epoxy resin-amine adducts and fatty acids have been known from EP 0 070 704 A2. There, amines and epoxy resins based on polyhydric phenols are used to prepare adducts having a molar mass of from 1000 g/mol to 3000 g/mol which are then reacted with unsaturated fatty acids to give a product in which the mass fraction of these fatty acids is from 25% to 50%. The amount of fatty acids is to be chosen so that all of the active amine hydrogen atoms are consumed.
In AT 390 261 B, emulsions of epoxy resin esters are disclosed which can be used as binders for air drying paints. The resins are prepared by reacting epoxy resins which are partially esterified with fatty acids, and copolymers of unsaturated fatty acids and (meth)acrylic acid, and further, copolymerisable monomers. The reaction products are at least partly neutralized using alkaline compounds to achieve water dilutability. These resins may also be admixed to amino functional epoxy resin esters.
Reaction products of reaction of epoxy resins, fatty acids, and amines have been known from EP 1 233 034 A1, and primers made therewith show good anti-corrosion properties. However, protective coatings made from such primers fail under extended exposure to corrosive environments, and their hardness is not sufficient.